Apparatus and a method for controlling a priority access and channel assignment call in a mobile telecommunication system

ABSTRACT

Disclosed is a method for controlling a PACA call in a mobile telecommunications system, which comprises: sending a new origination message from a mobile station in a PACA state to a base station; sending a service request message for a PACA call from the base station to a mobile switching center, requesting from the mobile switching center the base station to assign a traffic channel to the mobile station; assigning an available traffic channel to the mobile station to start a communication; and distinguishing the PACA call service from an ordinary call service.

PRIORITY

This application is a Divisional of U.S. application Ser. No.09/847,001, filed on May 1, 2001 now abandoned which claims priority toan application entitled “Method for Controlling a Priority Access andChannel Assignment Call in a Mobile Telecommunications System” filed inthe Korean Industrial Property Office on Jun. 1, 2000 and assignedSerial No. 2000-30012, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile telecommunication system, andmore particularly to an apparatus and a method for controlling apriority access and channel assignment call in a mobiletelecommunication system.

2. Description of the Related Art

Generally, the priority access and channel assignment (PACA) call is achannel assignment service provided to a subscriber. PACA allows asubscriber to obtain communication priority, so that when a userrequests a base station (BS) make a call to a mobile station that ispresently not available because its traffic channel is receiving toomuch traffic then the mobile station (MS) switches to a standby mode sothat it may be assigned to the traffic channel when the traffic channelis idle and available. Here, the standby mode of the MS is defined asthe “PACA state”, which is described in connection with FIGS. 1 and 2.

Referring to FIG. 1 there is illustrated a schematic diagram of aconventional mobile telecommunication system. It consists of a PublicSwitch Telecommunications Network (PSTN) 160, a Public Land MobileNetwork (PLMN) 150, a mobile switching center (MSC) 130, a home locationregister (HLR) 140, a base station controller (BSC) 120, a base station(BS) 110, and an MS 100. MS 100 communicates with both PSTN 160 and PLMN150. The BSC 120 performs both wired and wireless link control andhand-off. The BS 110 provides the wireless traffic channel to MS 100,which manages wireless traffic resources. The HLR 140 registers thesubscriber's location, although, not shown, the visitor locationregister (VLR) does the same function.

In FIG. 2, there is illustrated a flow diagram that depicts aconventional process for shifting the MS to the PACA state. MS 100 isrequested by the user to send a signal in step 211. If MS 100 does notrequest a signal be sent, then the signal stays at MS 100. In step 213,if MS 100 requests a signal be sent, MS 100 transmits an originationmessage to BS 110. BS 110 sends the signal as a call service requestmessage “CM_SERVICE,” REQ to MSC 130, in step 215. Then, if MSC 130sends an assign request message, “ASSIGN REQ” to BS 110 to assign atraffic channel for the origination message, in step 217, the BS 110detects an available or idle traffic channel, in step 219. If thereexists an idle traffic channel, the BS 110 assigns it to the MS 100, instep 221. However, if there is no idle traffic channel, the BS 110places the MS 100 in the PACA state. Then BS 110, sends a PACA messageto the MS 100, in step 225, while it also sends a channel assign failmessage, “CH_ASSIGN_FAIL” which represents failure in the attempt toassign a traffic channel to the MSC 130, in step 227.

Meanwhile, the MS 100 receives the PACA display message that states,“PACA-State” which informs the user, in step 229, that the MS 100 hasbeen shifted to the “PACA-State.” As previously stated, the PACA stateindicates that the BS 110 cannot assign an available traffic channel,with a communication priority, to the MS 100 because there is noavailable channel. MS 100 is placed on a standby mode for apredetermined time, for example 1 minute, to periodically re-send theorigination signal, until the BS 110 detects an idle traffic channelassigned to the MS. In this case, the BS 110 determines whether the MS100 has the communication priority or not, based on the subscriber'sinformation of the MS 100 contained in the assign request messagereceived from the MSC 130. Thus, if an idle traffic channel occurs inthe BS 110, the MS 100 is immediately connected to it from the PACAstate to establish a communication channel.

However, the aforementioned conventional method does not provide the MSC130 a method to distinguish when the MS 100 has been assigned to atraffic channel during the PACA state from the MS 100 that has beenassigned to a traffic channel through the ordinary assignment process,especially in charging the subscriber. In addition, when the MS 100 ishanded off from one BS to another, the former BS unnecessarily storesthe subscriber's information of the MS 100, thereby increasingconsumption of the resources. Moreover, when the MS 100 re-sends theorigination signal in the PACA state, the subscriber's information isadditionally stored and maintained in the BS, which also increasesconsumption of the resources as in handoff.

Therefore, a need exists for an apparatus and method that can beutilized to distinguish the MS that has been assigned to a trafficchannel during the PACA state from the MS that has been assigned atraffic channel through an ordinary assignment process. In addition,there exists a need for an apparatus and method that does not store asubscriber's information of a MS.

SUMMARY OF THE INVENTION

It is an oject of the present invention to provide a method forcontrolling a PACA call in a mobile telecommunication system, which maydistinguish the PACA call from the ordinary call in charging thecommunications services.

It is another object of the present invention to provide a method forcontrolling a PACA call in a mobile telecommunication system, which maydelete the PACA call information from the BS from which the MS is handedoff to a new BS, thereby improving the storage efficiency of the PACAbuffer.

It is still another object of the present invention to provide a methodfor controlling a PACA call in a mobile telecommunication system, whichmay delete the PACA call information previously stored in the BS whenthe MS in the PACA state, sends a new origination signal which isreceived and stored by the BS.

It is still another object of the present invention to provide a methodfor controlling a PACA call in a mobile telecommunication system, whichmay delete the PACA call information stored in the BS when the MSdeletes it, thereby improving the storage efficiency of the PACA buffer.

It is yet another object of the present invention to provide a methodfor controlling a PACA call in a mobile telecommunication system, whichmay send a busy tone signal to a caller who has sent a call signal tothe MS in the PACA state without requesting the MS to receive it.

According to the present invention, a method for controlling a PACA callin a mobile telecommunication system, comprises: sending a neworigination message from a mobile station in the PACA state to a basestation; sending a service request message for the PACA call from thebase station to a mobile switching center; requesting from the mobileswitching center that the base station assign a traffic channel to themobile station; assigning an available traffic channel to the mobilestation to start a communication; and distinguishing the PACA callservice from an ordinary call service.

The present invention will now be described more specifically withreference to the drawings attached only by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentinvention will become more apparent in light of the following detaileddescription of an exemplary embodiment thereof taken in conjunction withthe attached drawings in which:

FIG. 1 illustrates a schematic diagram that depicts the structure of aconventional mobile communication system;

FIG. 2 illustrates a flow diagram that depicts the process of shiftingan MS to the PACA state, according to the conventional method;

FIG. 3 illustrates a flow diagram that depicts shifting an MS to thePACA state and assigning a traffic channel thereto, according to thepresent invention;

FIG. 4 illustrates a flow diagram that depicts updating the PACA callinformation of the MSC, according to the present invention;

FIG. 5 illustrates a flow diagram that depicts handing off the PACAcall, according to the present invention;

FIG. 6 illustrates a flow diagram that depicts sending a reoriginationmessage for the PACA call;

FIG. 7 illustrates a flow diagram that depicts canceling the PACA call,according to the present invention; and

FIG. 8 illustrates a flow diagram that depicts controlling a call signaldirected toward the MS in the PACA state, according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the description, in connection with the drawings, there areomitted detailed descriptions of the conventional parts not required tocomprehend the technical concept of the present invention. The termsused in this specification are only to help understand descriptions ofthe essential functions connected with the invention, and should beinterpreted based on the meaning the whole specification intends toconvey including the attached claims.

Hereinafter described is the inventive system of controlling a PACA callin connection with FIGS. 1 and 3 to 7. There is a description of thefirst process of shifting an MS to the, PACA state “PACA_STATE” andassigning a traffic channel thereto with reference to FIG. 3. e MS 100is requested by the user to send a signal, in step 311, then it sendsthe signal in the form of an origination message to a BS 110, in step313. Then, the BS 110 sends an acknowledge order message,“BS_ACK_ORDER_MSG” to the MS 100, in step 315, and a communicationservice request message “CM_SERVICE_REQ” to the MSC 130, in step 317.The MSC 130 sends a subscriber's information request message“MS_CgVSvcingRQ_Msg” to the HLR 140/VLR (not shown) to request thesubscriber's information of the MS 100, in step 319. The HLR/VLRretrieves the subscriber's information loaded on a subscriber'sinformation response message, “MS_CgVSvcing” (PACA call flag) deliveredto the MSC 130, in step 321.

In this case, the subscriber's information response message containsstates, “PACA_Call_flag” which is set to have a predetermined value, forexample 1 if the MS has priority for the PACA call. The MSC 130 receivesthe subscriber's information response message, then sends a channelassign request message, “ASSIGNMENT_REQ” to request the BS 110 assign atraffic channel to the MS 100, in step 323. The channel assign requestmessage contains “queuing allowed” information to allow the PACA callbecause the subscriber's information represents priority for the PACAcall. Then, the BS 110 detects, in step 325, if there is an available oridle traffic channel to be assigned to the MS 100 to have a normalcommunication, in step 327.

In this case, if there is no idle traffic channel, the BS 110 places theMS 100 in the PACA state “PACA_STATE,” in step 329, then sends a channelassign fail message “Assignment_Fail” to the MSC 130, in step 331. Thechannel assign fail message states “PACA call queued” information, whichshows that the MS 100 has been shifted to the PACA state “PACA_STATE,”where information is stored in the PACA buffer of the BS 110. Although,not shown, the MSC 130 notifies the HLR 140/VLR that the MS 100 is inthe, PACA state “PACA_STATE.” Meanwhile, the BS 110 stores the PACA callof the MS 100 in the PACA buffer, sending, in step 333, a PACA callstorage message to the MS 100, which represents the address, forexample, “00000” of the PACA call queue message stored in the PACAbuffer. Whenever the address of the PACA call queue is changed, the BS110 sends the PACA call storage message to inform the MS 100 of thechanged address, for example “00001”, in step 335. Subsequently, if theBS 110 detects an idle traffic channel, in step 337, the MS 100 isnotified of it. Then, the MS 100 sends, in step 339, the reoriginationmessage to the BS 110, which in turn sends a communication servicerequest message “CM_SERVICE_REQ” to the MSC 130, in step 341. In thiscase, the communication service request message contains the PACAreorigination indicator “PACA_REORIG”, which indicates that thereorigination message is a PACA call. The MSC 130, sends in step 343,the subscriber's information request message to the HLR 140/VLR, which,in turn, sends the subscriber's information response message to the MSC130. Receiving the subscribcr's information response message, the MSC130 sends, in step 347, the channel assign request message to the BS 110to assign a traffic channel for the reorigination message to the MS 100in step 349. Then, the BS 110 sends the channel assignment message,“Channel_Assignment,” in step 351. After the MS 100 has completedcommunication, the MSC 130 distinguishes the PACA call service from theordinary call service in charging the subscriber based on the PACAreorigination indicator “PACA_REORIG” contained in the reoriginationmessage.

The process of updating the PACA call in the MSC is described inconnection with FIG. 4. Receiving an origination message, in step 411,the MSC 130 determines, in step 413, whether the origination message isthe PACA call or not. If not, the MSC 130 treats it as the ordinary callin step 415.

However, if the origination message is indicative of the PACA call, thenthe MSC 130 requests the HLR 140/VLR to send the subscriber'sinformation of the origination message, which is analyzed to determine,in step 417, whether the subscriber's registered location of theorigination message agrees with the registration of the HLR/VLR or not.If they do not agree, the MSC 130 determines if the MS 100 has beenhanded off from the previous BS to a new BS, then sends a first PACAcall update message to the previous BS. The first PACA call updatemessage requests the previous BS delete the PACA call information fromthe PACA buffer because the previous BS need not deal with it. Theprocess of dealing with the PACA call concerning the handoff of the MS100 will be described in connection with FIG. 5.

Meanwhile, if the subscriber's registered location of the originationmessage agrees with the origination message registered in HLR/VLR, thenthe MSC 130 determines whether the MS 100 is enabled for the“PACA_STATE” in HLR 140/VLR, in step 421. If the MS is enabled for thePACA state, the MSC 130 determines, in step 423, whether the cell ID ofthe origination message agrees with the origination message registeredin HLR/VLR. If they agree, the MSC 130 determines that the MS has sent anew origination message in the PACA state, then sends a second PACA callupdate message to the base station in step 425. The second PACA callupdate message requests the BS 110 delete the previous PACA call storedin the PACA buffer because of the new origination message. The processof dealing with the new PACA call generated from the MS 100 in the PACAstate “PACA_STATE” will be described in connection with FIG. 6.

Referring to FIG. 5 there is a description of the process of dealingwith the PACA call concerning the handoff of the MS 100 in connectionwith FIG. 5. The MS 100 sends the origination message to the first BS onrequest by the user, in step 511. Then, the first BS sends the BSacknowledge order message to the MS 100, in step 513, and thecommunication service request message to the MSC 130, in step 515. TheMSC 130, sends, in step 517, the subscriber's information requestmessage to HLR 140/VLR to retrieve the subscriber's information of theMS 100. The HLR/VLR loads the retrieved subscriber's information on thesubscriber's information response message delivered to the MSC 130, instep 519. The subscriber's information response message,“PACA_Call_flag” is set to have a predetermined value, for example 1 ifthe MS has priority for the PACA call.

The MSC 130 receives the subscriber's information response message, thensends a channel assign request message to request the first BS 110 toassign a traffic channel to the MS, in step 521. The channel assignrequest message contains “queuing allowed” information to allow the PACAcall, because the subscriber's information of the MS 100 representspriority for the PACA call. Then, the first BS 110 detects an availableor idle traffic channel. If there is no idle traffic channel, the firstBS determines that the MS 100 is in the PACA state “PACA_STATE,” whichindicates the storage of the origination message of the MS 100 as thePACA call in the PACA buffer. The PACA call is sent as a storage messagethat represents the address of the PACA call queue in the PACA buffer,for example “00000” to the MS 100, in step 523. In addition, the firstBS sends the channel assign fail message to the MSC 130, in step 525.The channel assign fail message contains the PACA call queuedinformation representing that the PACA state of the MS 100 has beenstored in the PACA buffer of the BS 110. Subsequently, the MSC 130receives the channel assign fail message, then sends the MS aninformation update message, “MS_CallReleaseRP PACA_STATE,” to VLR toupdate the information of the MS. The MS information update messagecontains the information representing that the MS 100 has been shiftedto the PACA state “PACA_STATE” stored in the PACA buffer.

Meanwhile, if the MS 100 is handed off from the previous BS (hereinafterreferred to as “first BS”) to another BS (hereinafter referred to as“second BS”), in step 529, it sends a new origination message containingthe PACA reorigination indicator “PACA_REORIG” to the second BS, in step531. Then, the second BS sends the BS acknowledge order message to theMS 100, in step 533, and the communication request message including thePACA reorigination indicator to the MSC 130, in step 535. The MSC 130,in turn, sends the subscriber's information request message to the VLRto provide the subscriber's information of the MS 100, in step 537. Thenthe VLR retrieves the subscriber's information loaded on thesubscriber's information response message delivered to the MSC 130, instep 539. In this case, the subscriber's information response messageincludes both the status information of the MS 100 being in the PACAstate and the location information of the MS 100 registered in the VLR.

Then the MSC 130 sends a first PACA update message to the first BS, instep 541. The first PACA update message is the message requesting thefirst BS to delete the PACA call stored in the PACA buffer of the firstBS because the MS 100 has been handed off from the first to the secondBS. Hence, the first BS sends the PACA update response message to the MSafter deleting the PACA call from the PACA buffer, in step 543. Then,the MSC 130 sends the channel assign request message to the second BS toassign a traffic channel, in step 545. The second BS sends the channelassign message to notify the MS 100 that a traffic channel has beenassigned to it, in step 547, so that the MS 100 performs an ordinarycommunication, in step 549. Terminating the communication, the MSC 130sends the information update message of the MS to the VLR to delete thePACA state information of the MS 100, in step 551.

Referring to FIG. 6, there is a description of the process of managingthe PACA call when the MS 100 sends a new PACA call in the PACA state“PACA_STATE.” If the MS 100, while being in the PACA state, in step 611,sends a new origination message containing the PACA reoriginationindicator, “PACA_REORIG” to the BS 110, in step 613, then the BS 110sends the BS response order message to the MS 100, in step 615. Then,the BS 110 sends the communication service request message containingthe, “PACA_REORIG” indicator to the MSC 130, in step 617, so that theMSC 130 sends, in step 619, the subscriber's information request messageto the VLR to obtain the subscriber's information. The VLR retrieves therequested subscriber's information loaded on the subscriber'sinformation response message delivered to the MSC, in step 621. In thiscase, the subscriber's information response message includes both thestatus information of the MS 100 being in the PACA state and thelocation information of the MS 100 registered in the VLR.

Then the MSC 130 sends a second PACA update message to the BS 110, instep 623. The second PACA update message is the message requesting theBS to delete the previous PACA call stored in the PACA buffer of the BSbecause the MS 100 has sent the new origination message requesting againthe PACA call. Hence, the BS 110 sends the PACA update response messageto the MS 130 after deleting the previous PACA call from the PACAbuffer, in step 625. Then, the MSC 130 sends the channel assign requestmessage to the BS 110 to assign a traffic channel, in step 627. Then,the BS 110 detects an available traffic channel to assign to the MS. IfBS 110 does not detect an available traffic channel, then the BS 110stores the PACA call into the PACA buffer, sending, in step 629, thechannel assign fail message containing the PACA call queued informationto the MSC 130. The MSC 130 sends the PACA call update message to theVLR to update the PACA state of the MS 100, in step 631. In addition,the BS 110 sends the PACA storage message containing the PACA call staterepresenting the storage location of the PACA call in the PACA buffer tothe MS 100, in step 633.

Describing the process of canceling the PACA call in connection withFIG. 7, the MS 100 detects the PACA call cancellation entered by theuser, in step 711. If MS 100 detects the PACA call cancellation enteredby the user, then the MS sends the PACA cancellation message to the BS110 in step 713, so that the BS 110 sends the BS response order messageto the MS 100, in step 715, which deletes the PACA call from the PACAbuffer. The PACA update message, indicates that the MS 100 has beenreleased from the PACA state to the MSC 130, in step 717. Then, the MSC130 sends, in step 719, the MS PACA update message “MS_PACAUpdateRP,”indicates that the MS 100 has been released from the PACA state to theVLR, and the PACA update response message to the BS 110, in step 721. Ofcourse, the PACA call may also be cancelled by the BS 110. Referring toFIG. 8, there is a description of the process of warding off a call fromthe MS in the PACA state in connection with FIG. 8. The MSC 130retrieves the receiving subscriber's information of the call detected,in step 811, to analyze it, in step 813, thereby determining, in step815, whether the receiving subscriber is in the PACA state or not. Ifthe receiving subscriber is in the PACA state, the MS 130 sends the busytone to the subscriber requesting the call, in step 817. Alternatively,if the receiving subscriber is not in the PACA state, the MSC 130 sendsa paging message to the BS 110 registering the receiving subscriber, instep 819, which in turn transfers it to the MS 100, in step 821. Then,the MS 100 sends the paging response message to the BS 110 in step 823,which in turn transfers it to the MSC 130, in step 825. Then, the MSC130 sends the channel assign request message to the BS 110, in step 827,so that the BS 110 assigns, in step 829, a traffic channel to the MS 100shifted to the communication stated, in step 831.

Thus, the present invention provides a mobile telecommunication systemwith means to distinguish the PACA call from the ordinary call incharging the communications services. In addition, the present inventiondeletes the PACA call information from the BS when the MS is handed offto a new BS or when the MS in the PACA state. Then, the presentinvention sends a new origination signal or when the MS BS cancels thePACA call, thereby improving the storage efficiency of the PACA buffer.Further, the present invention sends the busy tone signal to a callerwho has sent a call signal to the MS in the PACA state withoutrequesting the MS to receive it.

While the present invention has been described in connection withspecific embodiments accompanied by the attached drawings, it will bereadily apparent to those skilled in the art that various changes andmodifications may be made thereto without departing from the gist of thepresent invention.

1. A method for controlling a priority access and channel assignment(PACA) call in a mobile telecommunication system, the method comprising:determining whether a subscriber's registered location of an originationmessage agrees with the subscriber's registered location in a visitorlocation register (VLR); determining whether a mobile station is in aPACA state if the subscriber's registered location of the originationmessage agrees with that registered in the VLR; determining whether acell ID of the origination message agrees with that registered in theVLR if the mobile station is in the PACA state; determining that themobile station has sent a new origination message in the PACA state ifthe cell ID of the origination message agrees with that registered inthe VLR; sending a PACA call update message to a base station; anddeleting PACA call information for the mobile station from the basestation.
 2. A method as defined in claim 1, wherein the PACA callinformation deleted from the base station is previously stored in a PACAcall buffer of the base station.